Medical imaging systems and methods of using the same

ABSTRACT

A medical imaging system includes a collimator having a plurality of collimator parts configured to filter radiation emitted from a target object; a detector base; and a detector having a plurality of detector tiles, configured to acquire an image of the target object by detecting radiation that has passed through the plurality of collimator parts, wherein at least one of the plurality of detector tiles is tilted with respect to the detector base.

PRIORITY

This application is a divisional of U.S. patent application Ser. No.16/844,950 filed on Apr. 9, 2020, which claims priority to U.S.Provisional Application Ser. No. 62/832,082 filed on Apr. 10, 2019, bothof which are incorporated herein by reference in their entireties.

BACKGROUND

In medical imaging, such as molecular medical imaging (sometimes knownas nuclear medicine imaging), images representing radiopharmaceuticaldistributions may be generated for medical diagnosis. Prior to imaging,radiopharmaceuticals are injected into an imaging subject such as apatient. The radiopharmaceuticals emit radioactive photons, which canpenetrate through the body to be detected by a photon detector. Based oninformation from the received photons, the photon detector may thendetermine the distribution of the radiopharmaceuticals inside thepatient. Their distribution represents the physiological function of thepatient, and therefore images of their distribution provide valuableclinical information for diagnosis of a variety of diseases andconditions such as those in cardiology, oncology, neurology, etc.

To generate images, collimator and detector work in tandem. However,existing collimator and detector designs suffer from various issues. Forexample, detectors are conventionally organized in planar shapes toacquire data in a two-dimensional (2D) matrix format. Detectors oftenemploy large scintillator crystals coupled with photomultiplier tubes(PMTs) to detect radiations and record their positions. Thescintillator-based detector comprises the modules large in size and theposition of detected radiation is calculated by comparing the output ofneighboring modules. In some examples, the detector employs one piece ofscintillator, coupled with multiple PMTs. As a result, a detector isconventionally designed as one piece of a fixed shape and size oncedeployed (manufactured or installed). The deployment of rigid planardetectors provides a limited degree of spatial resolution and causesinflexibility to the imaging system, limiting system's capability ofoptimizing for different imaging tasks or subjects. Therefore,improvements on detectors for nuclear medicine imaging systems aredesired.

SUMMARY

According to various embodiments, the present disclosure provides amedical imaging system. The medical imaging system includes a collimatorconfigured to filter radiation emitted from a subject; and a detectorconfigured to detect radiation that has passed through the collimator,wherein the detector includes a plurality of detector tiles and at leastone detector tile is movable with respect to other detector tiles,wherein top surfaces of the plurality of detector tiles are capable tobe configured as being coplanar. In some embodiments, the collimatorincludes a plurality of collimator parts configured to be piece-wiseplanar. In some embodiments, each of the plurality of detector tiles ismovable. In some embodiments, each of the plurality of detector tileincludes a detector base. In some embodiments, the detector baseincludes a battery pack. In some embodiments, the battery pack iswireless chargeable. In some embodiments, the detector base includes awireless communication module. In some embodiments, the detectorincludes a plurality of detector bases, wherein one detector base isshared by at least two detector tiles. In some embodiments, the at leastone detector tile is configured to tilt an angle with respect to theother detector tiles. In some embodiments, the at least one detectortile is configured to tilt by an actuator. In some embodiments, thedetector is configured to change in shape by moving one or more detectortiles. In some embodiments, the detector is configured to changerotation and keep in shape by moving one or more detector tiles.

According to various embodiments, the present disclosure also provides amedical imaging system. The medical imaging system includes a pluralityof collimators configured to filter radiation emitted from a targetobject; and a detector configured to acquire an image of the targetobject by detecting the radiation that has passed through thecollimator, wherein a portion of the collimators is tilted with respectto a top surface of the detector. In some embodiments, another portionof the collimators is parallel to the top surface of the detector. Insome embodiments, the detector includes a plurality of detector tiles,wherein each detector tile is designated with a collimator. In someembodiments, the top surface of the detector is flat. In someembodiments, the portion of the collimators is tilted with an anglelarger than 3 degrees with respect to the top surface of the detector.In some embodiments, the medical imaging system further includes aplurality of shields between neighboring collimators.

According to various embodiments, the present disclosure also provides amethod for a method of acquiring a medical image. The method includesproviding a medical imaging system with a deformable detector, thedeformable detector including a plurality of detector tiles; determininga configuration of the deformable detector; moving a portion of theplurality of detector tiles, such that the deformable detector isconfigured to the determined configuration; and acquiring an image of atargeted subject by the deformable detector. In some embodiments, themethod further includes configuring a plurality of collimatorsassociated with the deformable detector.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 is a schematic diagram of an exemplary nuclear medicine imagingsystem according to various aspects of the present disclosure.

FIG. 2 is a cross-sectional view of part of an imaging system accordingto various aspects of the present disclosure.

FIG. 3 is a perspective view of an exemplary detector tile according tovarious aspects of the present disclosure.

FIG. 4 is a perspective view of an exemplary deformable detectoraccording to various aspects of the present disclosure.

FIGS. 5A-5D illustrate embodiment of a detector before and afterdeformation from a top view according to various aspects of the presentdisclosure.

FIGS. 6A-6D illustrate alternative embodiments of a detector before andafter deformation from a top view according to various aspects of thepresent disclosure.

FIG. 7 is a cross-sectional view of an imaging system with bendabledetector titles according to various aspects of the present disclosure.

FIG. 8 is a cross-sectional view of an imaging system with a planardetector and tilted collimator parts according to various aspects of thepresent disclosure.

FIG. 9 is a cross-sectional view of an imaging system with a planardetector and a planar collimator with tilted holes according to variousaspects of the present disclosure.

FIG. 10 is a flow chart of a method of examining a subject according tovarious aspects of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the disclosure.Specific examples of components and arrangements are described below tosimplify the present disclosure. These are, of course, merely examplesand are not intended to be limiting. Any alterations and furthermodifications to the described devices, systems, methods, and anyfurther application of the principles of the present disclosure arefully contemplated as would normally occur to one having ordinary skillin the art to which the disclosure relates. For example, the features,components, and/or steps described with respect to one embodiment may becombined with the features, components, and/or steps described withrespect to other embodiments of the present disclosure to form yetanother embodiment of a device, system, or method according to thepresent disclosure even though such a combination is not explicitlyshown. In addition, the present disclosure may repeat reference numeralsand/or letters in the various examples. This repetition is forsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Moreover, a feature on, connected to, and/or coupled to another featurein the present disclosure that follows may include embodiments in whichthe features are in direct contact, and may also include embodiments inwhich additional features may interpose the features, such that thefeatures may not be in direct contact. In addition, spatially relativeterms, for example, “lower,” “upper,” “horizontal,” “vertical,” “above,”“over,” “below,” “beneath,” “up,” “down,” “top,” “bottom,” etc., as wellas derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,”etc.) are used for ease of the present disclosure of one featuresrelationship to another feature. The spatially relative terms areintended to cover different orientations of the device including thefeatures. Still further, when a number or a range of numbers isdescribed with “about,” “approximate,” and the like, the term isintended to encompass numbers that are within a reasonable rangeincluding the number described, such as within +/−10% of the numberdescribed or other values as understood by person skilled in the art.For example, the term “about 5 cm” encompasses the dimension range from4.5 cm to 5.5 cm.

The present disclosure is generally related to the field of medicalimaging, and more particularly to the design of deformable detectorsused in nuclear medicine (molecular) imaging systems. The term“deformable” refers to being capable of changing shapes, geometries,areas, alignments and/or orientations.

In nuclear medicine (molecular) imaging systems, collimator and detectorwork in tandem to generate images that represent radiopharmaceuticaldistributions within a subject. However, existing collimator anddetector designs suffer from various issues. For example, detectors areconventionally organized in planar shapes to acquire planar projectionsof the object from multiple angles to reconstruct a three-dimensional(3D) image of the object. Conventional detectors employ largescintillator crystals coupled with photomultiplier tubes (PMTs) todetect radiations and record their positions. The scintillator-baseddetector comprises the modules large in size and the position ofdetected radiation is calculated by comparing the output of neighboringmodules. In some examples, the detector employs a continuous (one piece)scintillator, coupled with multiple PMTs. For example, a type ofmulti-anode PMT may have a fixed area of 52 cm×52 cm. Therefore, aconventional detector is designed as one module of fixed shape and sizeonce deployed (manufactured or installed). The deployment of rigidplanar detectors provides a limited degree of spatial resolution andcauses inflexibility to the imaging system.

The present disclosure provides new detector designs where a detectorincludes multiple detector modules (or detector tiles). Each modulefurther includes multiple cells and each cell acts individually togenerate images. The cell is also termed as a pixel. The detector maydeform, changing in shapes and/or sizes, by rearranging detector tiles.This deformable detector design provides flexibility to the imagingsystems, which helps with optimizing imaging performance for differenttargets and applications. Therefore, system performance may be improved.

Many medical imaging systems, for example, single photon emissioncomputed tomography (SPECT), computed tomography (CT), and positronemission tomography (PET) imagining systems, use one or more detectors,to acquire imaging data, such as gamma ray or photon imaging data. Priorto acquiring images, a radiopharmaceutical is usually taken orally orinjected into the patient. The radiopharmaceutical undergoes nucleardecay, emitting, either directly or indirectly through annihilation,gamma photons at certain rates and with characteristic energies. One ormore detector units are placed around the patient or object to record ormonitor emissions. In many cases, for convenience of manufacturing anddata processing, the detectors are organized in planar shape, thereforeacquire data in 2D matrix format, which are often referred to asprojections. Based the recorded information including position, energyand counts of such detected events, an image of the radiopharmaceuticaldistribution can be reconstructed to study the function of certain bodyparts.

FIG. 1 illustrates an exemplary nuclear medicine imaging system 100,which may be used to medically examine or treat a subject such as apatient. The imaging system 100 includes an integrated gantry 102 thatfurther includes a rotor 104 oriented about a gantry central bore 106.The rotor 104 is configured to support one or more detectors 108 (twodetectors 108 in opposing positions are shown). The rotor 104 is furtherconfigured to rotate axially about an axial axis (e.g., X-direction asshown). Each detector 108 works in tandem with a collimator 110. Thecollimator 110 is a device that guides photon path. In molecularimaging, photons may originate from unknown locations inside a subject,unlike in X-ray or CT where photons are emitted from a known source (orsources) position. Without collimators 110, photons from all directionsmay be recorded by detectors 108, and image reconstruction may becomedifficult. Therefore, collimators 110 are employed to guide possiblephoton paths so that images can be reconstructed, similar to the role oflens in a photography camera. The imaging system 100 further includes apatient table 112 coupled to a table support system 114, which may becoupled directly to a floor or may be coupled to the gantry 102 througha base. The patient table 112 is configured to be slidable with respectto the table support system 114, which facilitates ingress and egress ofa patient 150 into an examination position that is substantially alignedwith the axial axis. A control console 120 provides operation andcontrol of the imaging system 100, such as in any manner known in theart. For example, the control console 120 may be used by an operator ortechnician to control mechanical movements, such as rotating the rotator104, moving, rotating, or tilting the detectors 108 and collimators 110,and sliding the patient table 112. The imaging system 100 furtherincludes computer components (not shown), such as data storage units,image processors, image storage units, displays, which are for acquiringdata and reconstructing nuclear medicine images. In some embodiments,one or more computer components can be partially or entirely located ata remote location (e.g., on the cloud). In some embodiments, one of moreof these components may exist locally or remotely.

In some embodiments, the detector 108 is a semiconductor detector, suchas one based on cadmium telluride (CdTe), cadmium zinc telluride (CZT),or high purity germanium (HPGe). In some embodiments, the detector 108is a scintillator (such as sodium iodide (NaI) or caesium iodide (CsI)based) detector. In some other embodiments, the detector 108 may also bea scintillator coupled with compact photo multiplier tubes (PMTs),silicon photomultiplier tubes (SiPMT), or avalanche photodiodes. One ormore radiopharmaceuticals orally taken or injected into patient 150undergo nuclear decay and may emit, either directly or indirectlythrough annihilation, radiation (e.g., gamma photons) at certain ratesand with characteristic energies. The detector 108 is placed nearpatient 150 to record or monitor emissions. Based on recordedinformation such as position, energy, and counts of such detectedevents, an image of radiopharmaceutical distribution may bereconstructed to study the status or function of certain body parts onpatient 150.

The collimator 110 includes one or more openings, such as through holes.Depending on number and geometrical placement of through holes, thecollimator 110 may be a single-pinhole, multi-pinhole, coded aperture,or extended coded aperture (also known as spread field imaging, SFI)collimator, or other suitable types of collimator. Depending on profilesof through holes, the collimator 110 may be a parallel-hole, fan-beam,or cone-beam collimator, or other suitable types of collimator. Thecollimator 110 is placed between detector 108 and an imaging object,such as the patient 150, the openings on the collimators determining thedirections and angular span from which radiation can pass through toreach certain position on the detector.

In various embodiments, collimators are essentially perforated platesusually made of heavy metal such as lead and tungsten. In someembodiments, the collimator is made of planar plates, usually placed inparallel to the planar detector surface. The thickness of the plate,depending on the energy of photons it is designed to imaging, is largeenough to stop the majority of the radiation so that the photonsprimarily pass through the small pinholes on the plate. For example, forthe commonly used isotope, Technetium-99m (99mTc), emitting gamma rayswith energy around 140 keV, a 3 mm thickness is usually enough for aplate made of lead, and about 2 mm for tungsten. The thickness needs tobe greater to image higher energy gamma rays. These collimators need tobe place at certain distance from the detector to allow photons comingfrom the design field-of-view (FOV) passing the pinhole(s) to spreadacross the detector surface. A gap between a collimator and a detectorin this scenario is usually greater than 3 cm.

The imaging system 100 may include other necessary parts for an imaginggantry such as connectors that couple parts together (e.g., connectingdetector 108 and collimator 110 together), motors that cause parts tomove, photon shielding components, a housing component that containsother parts, etc. For example, a coupling and shielding component 116may connect detector 108 and collimator 110 such that both move (e.g.,rotate) together, and prevent radiation (photons) from reaching detector108 through paths other than collimator 110. In other embodiments,detector 108 and collimator 110 may move individually with respect toeach other.

FIG. 2 is a schematic cross-sectional view of a collimator 110 and adetector 108 work in tandem to generate images that representradiopharmaceutical distributions within a subject. In the illustratedembodiment, a coupling and shielding component 116 connects thecollimator 110 and the detector 108. The collimator 110 is positionedbetween the patient 150 and the detector 108 and configured to filterradiation by blocking certain photons and passing through other photons.Collimator 110 is made of radiation (e.g., photons) absorbing heavymetal(s) or alloy, such as lead and/or tungsten. Collimator 110 hasopenings 118 built therein to allow some photons to pass through andreach detector 108. It should be understood that radiation or photonblocking or absorption by a collimator does not require blocking of 100%of photons because a small percentage of photons (e.g., 5% or less) maystill penetrate through the full thickness of the radiation absorbingmaterial. The number of escaping photons may decrease exponentially withthe thickness of a collimator. In other words, blocking (or othersimilar terms) means that substantially all of the photons (e.g., 95% ormore, or 99% or more) are absorbed by the radiation absorbing material.

Openings 118—which may also be called through holes, tunnels, apertures,or pass-through features—may have any suitable shape, size, number,and/or distribution within their respective collimators. In someembodiments, openings 118 may include parallel holes, fan beams, conebeams, slit-slat, pinholes, multi-pinholes, coded aperture, any othersuitably shaped openings, or combinations thereof. In some embodiments,collimator 118 is placed close (e.g., 2 cm or less) to patient 150.Thus, collimator 108 may use parallel holes or fan-beams (converging ordiverging) since such features do not need significant separation frompatient 150. In some embodiments, openings 118 may be slanted,converging, or diverging and may form fan beams or cone beams, etc. Inan example, openings 118 include a plurality of pinholes, where thenumber of pinholes may be greater than 11, greater than 23, or greaterthan 59, or greater than 83. Openings 118 may form a coded aperturepattern, for example, an MURA (modified uniformly redundant array) ofsizes 5, 7, 11, and 13 comprise 12, 24, 60, and 84 holes, respectively.A higher number of pinholes helps improve imaging sensitivity. Further,openings 118 may be single pinhole, multi-pinhole, multiple pinholemodules (including spread field imaging (SFI) or coded aperture).

Still referring to FIG. 2, a photon may hit a top surface of collimator110 with an acceptable incident angle (denoted by symbol α in FIG. 2 asan angle between line A1 and the vertical direction Z where line A1 isthe travel direction of the photon and direction Z is the normal of thetop surface of collimator 110). If the incident angle is greater than apredetermined threshold value, the photon would be absorbed bycollimator 110 (note there are occasions where the photon cuts through aportion of collimator 110 adjacent the opening (e.g., a thin area on thesidewall of the opening)). Therefore, the acceptable incident angle arepresents the range of possible incident angles for photons to passthrough an opening 118 without cutting through a portion of collimator110.

In some embodiments, this threshold value ranges from 0° to about 2° orfrom 0° to about 10°. In an example, a LEHR (low energy high resolution)collimator has an opening diameter of about 1.11 mm and a length ofabout 24.04 mm, with an acceptable incident angle range of 0° to about2.64°. In another example, a GAP (general all purpose) collimator has anopening diameter of about 1.40 mm and a length of about 25.4 mm, with anacceptable incident angle range of 0° to about 3.15°). In yet anotherexample, a LEHS (low energy high sensitivity) collimator has an openingdiameter of about 2.54 mm, a length of about 24.04 mm, with anacceptable incident angle range of 0° to about 6.03°. The acceptableincident angle for collimator 110 is often less than 10°. Photons thatcan pass through collimator 110 is considered within a field-of-view(FOV) of collimator 110 (denoted in FIG. 2 as a space within lines A1and A2).

In various embodiments of the present disclosure, the detector 108 areformed by multiple detector modules, which is also referred to asdetector tiles or pixelated detectors. For example, the detector 108 mayinclude twenty detector tiles arranged to form a rectangular array offive rows of four detector tiles. Each detector tile individuallyfunctions as a mini detector to capture or record emissions. At leastone detector tile or each detector tile is movable with respect to otherdetector tiles, which reconfigures the detector 108 to form differentshapes and/or sizes.

FIG. 3 illustrates an exemplary detector tile 200. The detector tile 200may be formed of any semiconductor material as known in the art, forexample, cadmium zinc telluride (CdZnTe), often referred to as CZT,gallium arsenide (GaAs) and silicon multiplier (SiPM), among others.Specifically, the detector tile 200 include a crystal 202 formed fromthe semiconductor material and mounted on a detector base 214. Thebottom surface of the crystal 202 includes an array of pixels 212, suchas a rectangular array, a square array, or other suitable arrays. Thepixels 212 may be of substantially the same size and also may berectangular or square in shape. The size of the pixels 212 may rangefrom about 1×1 mm² to about 4×4 mm² in various embodiments. The pixelpitch P of the array may range from less than 1 mm to about 6 mm invarious embodiments. Further, in the same array, different pixels 212may have different sizes or geometries. For example, a portion of thepixels 212 in the center of the array may be larger than the peripheralones, or vice versa. Also, the number of pixels 212 may be greater orsmaller than 16 (4×4) as shown in FIG. 3, for example, 256 (16×16)pixels 212 may be provided. It also should be noted that the thicknessof the crystal 202 may vary between several millimeters to severalcentimeters. The size of the detector tile 200 may range from about 4cm×4 cm to about 10 cm×10 cm in various embodiments, such as 5 cm×5 cm.And the shape of detector tile does not have to be square, and can berectangle, hexagon, etc. In a specific example, a CZT or siliconmultiplier (SiPM) based detector tile 200 is fabricated in a size of 4cm×4 cm, further consisting of an array of 16×16 pixels of a unit pixelsize of 2.5 mm×2.5 mm. In operation, each pixel 212 records or monitorsindividually the amount of emission arrived and generates signals (e.g.,voltage or current) in association with the amount of emission. In someembodiments, the detector base 214 includes appropriate electroniccircuits (e.g., ASICs) to collect and process the signals from thepixels 212.

The detector base 214 may include wired connection units, for example,bus lines (not shown) to transmit singles from the ASICs to the controlmodule 120 (FIG. 1). Alternatively, the detector base 214 may includewireless connection units using technologies such as WiFi and/orBlue-tooth, to avoid additional wiring that may cause complicationduring detector deformation. Furthermore, the detector base 214 mayinclude one or more battery packs to further reduce wiring. The batterypacks can be charged during system downtime. The detector base 214 mayalso include wireless charging units that allow the battery packs to becharged wirelessly. In one example, the detector tile 200 totallyeliminates wire connections, relying on wireless data transmission andwireless charging for respective functions. As will be discussed below,multiple detector tiles 200 will jointly form a deformable detector withat least one or each detector tile 200 movable with respect to others.Each of the detector tiles may carry their own battery packs.Alternatively, the battery packs can be mounted to some of the detectortiles that is movable, while the other detector tiles that are fixed canhave wire connections to supply power instead of battery packs.

FIG. 4 illustrates a detector 108 that includes a plurality, forexample, 24 detector tiles 200 arranged to form a rectangular array offour rows of six detector tiles. It should be noted that the detector108 may have larger or smaller arrays of detector tiles 200 than asillustrated. Adjacent detector tiles 200 may leave a gap smaller than apredetermined width, such as smaller than a width of a single detectortile 200. The gap may be as small as possible, for example, asphysically achievable. In a specific example, the gap is about 5% toabout 20% of a single detector tile 200's width. In another example, thegap is less than one pixel pitch P (FIG. 3) or one detector resolutionof a detector tile 200, but larger than zero. Alternatively, adjacentdetector tiles 200 may be in physical contact (abut) with each other.

Among the detector tiles 200, at least one detector tile 200 may bemounted on a track (e.g., slides or rails). The track is configured toallow that detector tile 200 to move with respect to other detectortiles, thereby changing a contoured geometry of the detector 108. Theimaging system may employ robotic arms, with fingers attached to themovable detector tiles 200. Alternatively, each detector tile 200 may beindividually movable along the tracks with respect to each other. Insome embodiments, the detector 108 may include at least threeindividually movable groups, such as three, four, five, or six movabledetector tiles. In furtherance of some embodiments, detector tiles 200come with different sizes and/or geometries. For example, one detectortile may be larger than another, or one detector tile has a square shapewhile another has a rectangular shape. Further, multiple detector tiles200 may form a group that moves as one unit. Inside the group, locationsof the detector tiles 200 are fixed. In furtherance, detector tiles 200assigned to the same group may share a single battery pack, instead offor each detector tile to carry its own battery pack. And instead oftransforming freely, the detector 108 may transform into a few shapesthat are predetermined for certain imaging tasks. Thus, a detector 108may be divided in to a plurality of movable groups with different sizesand/or geometries. In some embodiments, the detector 108 may include atleast three individually movable groups, such as three, four, five, orsix movable detector tiles. Each individually movable group may includeone or more detector tiles 200 with positions relatively fixed insidethe group. In furtherance of some embodiments, the smallest movablegroup consists of only one detector tile 200. In the illustratedembodiment, the top surfaces of all the detector tiles (individuallymovable or inside a movable group) in a detector 108 are capable to beconfigured as being coplanar, and in that form the detector tiles areoperating as one unity, and image acquired by the detector tiles isstored or represented as one entity such as in the form of one array orone matrix.

FIGS. 5A-5D are top views of the detector 108 in the imaging system 100in FIG. 1. FIGS. 5A-5D illustrate two embodiments of rotating arectangular detector without changing its shape or aspect ratio(length/width). FIGS. 5A and 5B illustrate mechanically rotating thedetector 108 as a whole. The X-direction marks the axial axis that thepatient 150 from head-to-toe lies along. Besides the rotor 104, whichprovides the rotation of the detector 108 around the axial axis, theimaging system 100 may further has a rotating mechanism mounted on therotor 104, which allows the detector 108 to rotate around the normaldirection of its own. For example, for a detector of size 40 cm×50 cm,the short side (40 cm) is usually aligned with the axial axis in a topview in conventional orientation so that the long side (50 cm) providesmaximal coverage in lateral direction (Y-direction) because conventionalSPECT systems equipped with a parallel hole collimator provides a FOV of50 cm diameter. In FIG. 2B, the detector 108 rotates 90 degrees in theX-Y plane around its center, such that the long side is aligned with theaxial direction instead, to provide different FOV along axial axis andin cross-sectional plane. In this orientation, the system provides morecoverage along the axial direction. One benefit of such orientation isthat whole body image may be acquired in smaller number of bed position.

As a comparison, FIGS. 5C and 5D illustrate an example of a deformabledetector 108. The deformable detector 108 of size 40 cm×50 cm includesthree detector tiles 108-I, 108-II, and 108-III (alternatively, each of108-I/II/III may include multiple grouped smaller detector tiles). Thedetector tiles 108-I and 108-III each has a dimension of 5 cm×40 cm, andthe detector tile 108-II has a dimension of 40 cm×40 cm. The centerdetector tile 108-II is fixed, while the other two smaller detectortiles 108-I and 108-II are movable with respect to the center detectortile 108-II. In the illustrated embodiment, the detector tile 108-Islides (e.g., being pushed by a robotic arm) counterclockwise from thetop of the center detector tile 108-II to its left side. Similarly, thedetector tile 108-II slides counterclockwise from the bottom of thecenter detector tile 108-II to its right side. The reassembled detector108 keeps the same shape and size of 40 cm×50 cm but changes itsalignment equivalently as after a 90 degrees rotation in the X-Y plane,similar to its counterpart shown in FIG. 5B.

FIGS. 6A and 6B illustrate another example in which a detector 108 maydeform into a different shape, with a different aspect ratio. Theillustrated example demonstrates a way to transform a detector of size40 cm×60 cm to 30 cm×80 cm. The detector 108 includes three detectortiles 108-I, 108-II, and 108-III (alternatively, each of 108-I/II/IIImay include multiple grouped smaller detector tiles). The detector tiles108-I and 108-III each has a dimension of 10 cm×30 cm, and the detectortile 108-II has a dimension of 30 cm×60 cm. The center detector tile108-II is fixed, while the other two smaller detector tiles 108-I and108-III are movable with respect to the center detector tile 108-II.During transformation, the moving paths and directions of detector tiles108-I and 108-III are denoted with doted arrows. The long edge (30 cm)of the movable detector tile 108-I or 108-III aligns with the short edge(30 cm) of the detector tile 108-II after the transformation. Thereassembled detector 108 keeps the same detector area of 2400 cm², butwith an elongated shape and a different aspect ratio (from 60/40 to80/30).

Different ways of transformation exist. For example, as shown in FIGS.6C and 6D, detector tile 108-I and 108-III can be rotated and attachedto the same side of the detector to achieve the same transformation.During transformation, the moving paths and directions of detector tiles108-I and 108-III are denoted with doted arrows. Under the similarprinciple as disclosed herein, depending on sizes of detector tiles orgrouped detector tiles, the detector 108 may deform into various othershapes and aspect ratios. For example, a 40 cm×60 cm detector may deforminto a 30 cm×80 cm detector as shown in FIGS. 6B and 6C, or a 50 cm×48cm or a 25 cm×96 cm detector. And this kind of deformation can be easilyimplemented with detector tiles.

In the illustrated embodiments above, the detector tiles are configuredto keep coplanar such that the surface of the detector 108 remains flat.Meanwhile, the detector tiles (or groups of detector tiles) may also beconfigured to form angles, such as by tilting. FIG. 7 illustrates across-sectional view of the imaging system 100 with deformable detector108 in yet another embodiment. In previous embodiments, before and afterthe transformation, top surfaces of the detector tiles of the detector108 are kept coplanar. Besides transforming the detector 108 planarly,the detector tiles may also be tilted by an angle, such as angles β1 andβ2 for detector tiles 108-I and 108-II, respectively. In someapplications such as imaging a heart 152, the object of imaging isrelatively small compared with the detector size. Imaging heart is animportant clinical application of SPECT, accounting for about 60% ofSPECT scans in the US. In this application, the detector may be bent bybeing partitioned into several tilted detector tiles. A human heart isusually 12 cm long and 10 cm wide, which is much smaller than theconventional detector size of about 40 cm×50 cm. Because the size of aheart is much smaller than the detector, collimators 110-I and 110-IImay be designed in two parts which form a small angle β such as 6degrees, 8 degrees, 10 degrees, or 12 degrees, to acquire projections attwo slightly different angles. In some embodiments, the maximum angle βis limited to be less than about 40 degrees or about 60 degrees. Thecollimators 110-I and 110-II in such placement is termed angularlyplaced collimators. The FOV of such angularly placed collimators areoverlapping. In some embodiments, the normal lines of these collimator(lines perpendicularly passing through the center of the collimators,denoted as dotted lines C1 and C2 in FIG. 7) intersect at one commonpoint P₀ (or a relatively small volume in space where the organlocated), which defines the center of FOV of the system in suchconfiguration.

The images of the heart 152 may be projected through the two collimators110-I and 110-II onto two separate tiles of the detector 108. There is ashielding plate 116 between the two tiles of the detector 108,preventing cross-talk between the two parts, i.e., radiation passingthrough one collimator and hitting the other tile of the detector. Tobetter receive signals, the detector may be split into two detectortiles which bend slightly so that each tile is parallel to thecollimator surface.

Actuators 216 may be used to elevate (tilt) one edge of the detectortile 108-I or 108-II, or both. In some embodiments, actuators 216extends from the detector base 214. In the illustrated embodiment, thetilted detector tiles 108-I and 108-II form small angles β1 and β2 withrespect to the top surface of the detector base 214. Angles β1 and β2may be the same or different, with the relationship of β1+β2=β. In aspecific example, β is 6 degrees, β1 is 2 degrees, and β2 is 4 degrees.By titling detector tiles 108-I and 108-II in different angles, theprecise position of the common point P₀ can be finely tweaked. The otheredges of the detector tiles 108-I and 108-II may stay abut, or have asmall gap (e.g., a gap width smaller than a width of the detector tile,or less than 10 cm) in between. In the illustrated embodiment, the twoedges may be linked by a hinge 220 and considered as still in physicalcontact. If the two edges stay in physical contact, the two detectortiles 108-I and 108-II may share one common detector base 214, insteadof two separate detector bases, as shown in FIG. 7. In furtherance ofthe embodiment, if the detector 108 includes three or more tilteddetector tiles, the tilted detector tiles may still share one commondetector base 214.

The collimators 110-I and 110-II in this case may be pinhole,multi-pinhole, coded aperture, or other suitable forms. One benefit ofthis design is that multiple projections of the object can be acquiredat one detector position. If original imaging requires 60 projections byrotating detector to 60 positions, now it can be done with 30 detectorpositions. On a dual opposing detectors system which is common forclinical systems (e.g., imaging system 100 in FIG. 1), 60 projectionsrequire rotating the two opposing detectors to 30 positions each, now itcan be done with only 15 detector positions of the two opposingdetectors, reducing imaging time to half.

In some embodiments, the collimators 110-I and 110-II are separatedpieces. For example, the collimator 110-I is mounted to the detectortile 108-I such that both move (e.g., rotate or tilt) together, andsimilarly the collimator 110-II is mounted to the detector tile 108-II.Therefore, when the actuators 216 extend to tilt the detector tiles,each collimator is tilted accordingly together with the respectivedetector tile. In alternative embodiments, the collimators 110-I and110-II are fabricated as one piece with a fixed angle β. The detectortiles 108-I and 108-II are tilted first without the collimatorsattached. After the detector tiles 108-I and 108-II have been tilted tothe predetermined angle (β1+β2=β), the collimators 110-I and 110-II arethen mounted above thereafter manually or automatically with roboticarms.

In some other embodiments, the detector 108 may stay planar withoutbeing bent or tilted, while the collimator 110 comprises multiple partsthat are positioned at small angles and there are portions of thedetector that are designated to receive radiations from each of theseparts of collimator (these designated portions of detector may overlapslightly), such as shown in FIG. 8. Similar to what has been discussedabove in association with FIG. 7, the FOV of such angularly placedcollimators are overlapping. In some embodiments, the normal lines ofthese collimators (lines perpendicularly passing through the center ofthe collimators, denoted as dotted lines C1, C2, and C3 in FIG. 8)intersect at one common point (or a relatively small volume in spacewhere the organ located), which defines the center of FOV of the systemin such configuration. In the illustrated embodiment, imaging can bedone in one third of the original detector rotations. Since the designworks in the case of detector not bending, this design works withconventional systems employing detectors that are not bendable, makingit applicable to current systems that employ unbendable detectors. Notethat in this embodiment, the collimator parts 110-I/II/III may not beparallel to the detector surface. Here “not be parallel” is referred toas having an angle formed between the collimator and the detectorsurfaces that is larger than the tolerance of mechanical assemblyinaccuracy, such as an angle larger than 1 degree, or an angle largerthan 3 degrees. The collimator 110 (including collimator parts110-I/II/III) is considered as piece-wise planar, such that eachcollimator part is planar, while some adjacent collimator parts(portions with holes) are not coplanar. The collimator 110 may befabricated as one piece, or as two or three separate pieces and mountedseparately. Since the detector 108 does not bend, it may be easier justmaking the collimator 110 as one piece, and there may be still shieldingplates 116 in between to separate the collimator parts 110-I/II/III,preventing radiations passing though one collimator and hitting portionsof detector designated to receive radiations passing through anothercollimator.

In yet another embodiment, similar to the previous embodiment, but thecollimator may be in planar shape, and comprises multiple parts and eachpart with a group of holes that are tilted by a small angle, andpointing to the designed FOV, as shown in FIG. 9. In this case, thecollimator surface may be parallel to the detector surface that may bein planar shape as well. And the holes in each collimator part (110-I,II, or III) may be parallel to each other. In the illustratedembodiment, holes in the collimator parts 110-I and 110-III are tilted,such that dotted lines C1 and C3 through centers of respectivecollimator parts and parallel to holes' elongated direction intersect atcommon point P₀. While holes in the middle collimator part 110-II extendalong its normal direction, such as the holes shown in FIG. 2 andrespective dotted line C2 through the center of the middle collimatorpart extends along the normal direction and goes through common point P₀as well.

Referring now to FIG. 10, a flow chart of a method 500 for acquiring asubject image with deformable detector is illustrated according tovarious aspects of the present disclosure. The method 500 is merely anexample and is not intended to limit the present disclosure to what isexplicitly illustrated in the method 500. Additional operations can beprovided before, during, and after the method 500, and some operationsdescribed can be replaced, eliminated, or moved around for additionalembodiments of the method. The method 500 is described below inconjunction with FIGS. 1-8.

At operation 502, a medical imaging system equipped with at least onedeformable detector is provided. The deformable detector furtherincludes multiple detector tiles. The medical imaging system, deformabledetector, and detector tiles are similar to the imaging system 100illustrated in FIG. 1, the deformable detector 108 illustrated in FIG.4, and the detector tile illustrated in FIG. 3. Similar aspects are notrepeated below in the interest of conciseness.

At operation 504, a preferred shape, orientation, and/or area of thedeformable detector is determined. The consideration may include sizeand/or shape of the targeted subject, such as a patient, or a particularorgan or body part of the patient. The other consideration may includedistance from the targeted subject to the detector. In some embodiments,operation 504 picks from a group of predetermined detectorconfigurations.

At operation 506, the detector rotates along its normal axis(perpendicular to the detector), or a portion of the detector tiles aremoved, such as by moving the selected detector tiles along tracks. Forexample, operation 506 may only need to move one detector tile, whileother detector tiles remain fixed. Or, two or more detector tiles wouldbe moved. Or, all detector tiles will be moved. Operation 506 may alsobatch a few detector tiles in a group, such that detector tiles belongedto the same group are moved together while remain relatively fixed toeach other within the group. In one embodiment, the top surfaces of thedetector tiles are configured to be coplanar during deformation, inother words, the top surface of the deformable detector is kept flat(also termed as the deformable detector is planar), while the shape(e.g., geometry or aspect ratio is changed as in FIGS. 6A-6D) and/ororientation (e.g., same shape but rotated as in FIGS. 5C and 5D) ischanged. In another embodiment, one or more detector tiles are moved toedges of the deformable detector, or moved away from the other part ofthe deformable detector at a certain distance, or moved to stack behindother detector tiles, and shut off, which equivalently reduces effectivearea of the deformable detector. In yet another embodiment, a portion ofthe detector tiles are tilted to form a non-flat detector, such asillustrated in FIG. 7.

At operation 508, collimators associated with the deformable detectorare configured. In one embodiment, each collimator is fixed to therespective detector tile, such that the collimator is moved or tiltedtogether with the detector tile mounted thereon. Alternatively, thecollimators may be assembled or mounted above the detector tiles afterthe detector deformation is completed.

At operation 510, the medical imaging system acquires images of thetargeted subject by detecting or monitoring amount of radiationcollected by the deformable detector. An image processing unit in themedical imaging system may perform an image reconstruction based on theraw images acquired from the deformable detector.

Although not intended to be limiting, one or more embodiments of thepresent disclosure provide many benefits for molecular imaging of asubject such as a patient. For example, the deformable detectors allowan imaging system to gain flexibility in spatial resolution and increasestep-and-scan efficiency when acquiring 3D images. Therefore, systemperformance is improved.

The foregoing outlines features of several embodiments so that those ofordinary skill in the art may better understand the aspects of thepresent disclosure. Those of ordinary skill in the art should appreciatethat they may readily use the present disclosure as a basis fordesigning or modifying other processes and structures for carrying outthe same purposes and/or achieving the same advantages of theembodiments introduced herein. Those of ordinary skill in the art shouldalso realize that such equivalent constructions do not depart from thespirit and scope of the present disclosure, and that they may makevarious changes, substitutions, and alterations herein without departingfrom the spirit and scope of the present disclosure. Accordingly, it isappropriate that the appended claims be construed broadly and in amanner consistent with the present disclosure.

What is claimed is:
 1. A medical imaging system, comprising: acollimator having a plurality of collimator parts configured to filterradiation emitted from a target object; a detector base; and a detectorhaving a plurality of detector tiles, configured to acquire an image ofthe target object by detecting radiation that has passed through theplurality of collimator parts, wherein at least one of the plurality ofdetector tiles is tilted with respect to the detector base.
 2. Themedical imaging system of claim 1, wherein each of the plurality ofdetector tiles has a field of view and the fields of view overlap. 3.The medical imaging system of claim 1, further comprising at least oneshielding plate positioned between the plurality of detector tiles. 4.The medical imaging system of claim 1, wherein the at least one tilteddetector tile is tilted by an actuator positioned between the detectorbase and the at least one tilted detector tile.
 5. The medical imagingsystem of claim 1, wherein the plurality of collimator parts arehingedly linked.
 6. The medical imaging system of claim 1, wherein atleast one of the plurality of collimator parts includes through holesthat form a coded aperture or an extended coded aperture.
 7. The medicalimaging system of claim 1, wherein each of the plurality of collimatorparts is mounted to a respective one of the plurality of detector tilessuch that each of the plurality of collimator parts moves with itsrespective detector tile.
 8. The medical imaging system of claim 1,wherein each of the plurality of detector tiles corresponds to one ofthe plurality of collimator parts, and wherein at least one of theplurality of collimator parts is not parallel with respect to a topsurface of its corresponding detector tile.
 9. A medical imaging system,comprising: a plurality of collimators configured to filter radiationemitted from a target object; and a detector configured to acquire animage of the target object by detecting the radiation that has passedthrough the plurality of collimators, wherein at least one of theplurality of collimators is tilted with respect to a top surface of thedetector.
 10. The medical imaging system of claim 9, wherein at leastanother one of the plurality of collimators is parallel to the topsurface of the detector.
 11. The medical imaging system of claim 9,wherein the detector includes a plurality of detector tiles, whereineach detector tile is designated with one of the plurality ofcollimators and the top surface of the detector is flat.
 12. The medicalimaging system of claim 9, wherein at least one of the plurality ofcollimators includes through holes that form a coded aperture or anextended coded aperture.
 13. The medical imaging system of claim 9,wherein at least one of the plurality of the collimators is tilted withan angle larger than 3 degrees with respect to the top surface of thedetector.
 14. The medical imaging system of claim 9, further comprisinga plurality of shields between neighboring collimators.
 15. The medicalimaging system of claim 9, wherein the plurality of collimators arefabricated as one piece.
 16. A medical imaging system, comprising: atleast one collimator configured to filter radiation emitted from atarget object, wherein the at least one collimator has a plurality ofcollimator parts, each collimator part having a group of holes angledtowards a field of view, wherein the group of holes in at least one ofthe collimator parts form a coded aperture or an extended codedaperture; and at least one detector configured to acquire an image ofthe target object by detecting the radiation that has passed through thecollimator.
 17. The medical imaging system of claim 16, wherein a topsurface of the at least one collimator is parallel to a top surface ofthe detector.
 18. The medical imaging system of claim 16, wherein theholes in each of the groups of holes are parallel to each other.
 19. Themedical imaging system of claim 16, wherein the holes in each of thegroups of holes are angled towards a common point within the field ofview.
 20. The medical imaging system of claim 16, further comprisingshielding plates positioned between the plurality of collimator parts.